Le 13/10/2021 à 09:09, Kees Cook a écrit :
On Mon, Oct 11, 2021 at 05:25:36PM +0200, Christophe Leroy wrote:
Behind a location, lkdtm_EXEC_RODATA() executes a real function,
not a copy of do_nothing().
So do it directly instead of using execute_location().
I don't understand this. Why does the next patch not fix this?
Well, probably it would, but it looked incorrect in my mind.
lkdtm_rodata_do_nothing() is a function which has its own function
descriptor, it is not a copy of do_nothing().
If we use execute_location() as modified by next patch, then we will
execute it using the function descriptor of do_nothing(). Allthough it
most likely works (at least on powerpc as it uses the same TOC) it looks
odd to me to do so.
Am I missing something ?
Christophe
-Kees
And fix displayed addresses by dereferencing the function descriptors.
Signed-off-by: Christophe Leroy <christophe.leroy@xxxxxxxxxx>
---
drivers/misc/lkdtm/perms.c | 9 ++++++++-
1 file changed, 8 insertions(+), 1 deletion(-)
diff --git a/drivers/misc/lkdtm/perms.c b/drivers/misc/lkdtm/perms.c
index 442d60ed25ef..da16564e1ecd 100644
--- a/drivers/misc/lkdtm/perms.c
+++ b/drivers/misc/lkdtm/perms.c
@@ -153,7 +153,14 @@ void lkdtm_EXEC_VMALLOC(void)
void lkdtm_EXEC_RODATA(void)
{
- execute_location(lkdtm_rodata_do_nothing, CODE_AS_IS);
+ pr_info("attempting ok execution at %px\n",
+ dereference_symbol_descriptor(do_nothing));
+ do_nothing();
+
+ pr_info("attempting bad execution at %px\n",
+ dereference_symbol_descriptor(lkdtm_rodata_do_nothing));
+ lkdtm_rodata_do_nothing();
+ pr_err("FAIL: func returned\n");
}
void lkdtm_EXEC_USERSPACE(void)
--
2.31.1
